I propose to analyze the course of meiosis in spermatocytes of three different kinds of organisms which have evolved unusual modes of chromosome distribution. Each organism violates the "law" of random segregation of chromosomes in a different way, and, therefore, each represents a non-repeatable "natural experiment" in the control of chromosome distribution. These organisms are: (1) certain neuropteran insects, in which unconnected chromosomes are faithfully passed to opposite poles at the first meiotic division, (2) certain spiders, in which unconnected chromosomes are passed to the same pole at meiosis I, and (3) a mole cricket, in whose spermatocytes a heteromorphic bivalent and a single X chromosome are separated non-randomly with respect to each other at anaphase I. Meiosis in these three kinds of organisms will be analyzed by time-lapse cinematography, by micro-manipulation, and by electron microscopy. It is possible that the mechanisms of these unusual modes of chromosome distribution have arisen through modification of a component (or components) of the more orthodox meiosis of most other higher organisms. In this case, a careful study of meiosis in these animals will yield information about the mechanism of the orthodox meiosis not obtainable by any other means. However, should the mechanisms of these unorthodox modes of chromosome distribution prove to be totally unexpected and unpredictable, they would be the more interesting.